An optical disc of this invention is configured to be capable of dealing with both information in HD DVD and information in DVD. The optical disc is basically specified by the following items (1) to (7): (1) the optical disc is a single-sided dual layer optical disc where a light transmission layer, a first recording layer accessed with a first laser beam, an space layer, and a second recording layer accessed with a second laser beam are arranged in that order in the direction in which the laser beam enters, (2) the areal recoding density of the second recording layer is three times or more as high as that of the first recording layer, (3) identifying information which indicates that the first recording layer has been formed is formed in the second recording layer, (4) the distance in the light transmission layer from the incidence plane to the first recording layer is 550 μm or more, (5) the distance in the light transmission layer from the incidence plane to the second recording layer is 622 μm or less, (6) the reflectivity of the first recording layer with respect to the first laser beam is 45% to 65%, and (7) the reflectivity of the second recording layer with respect to the second laser beam is 15% to 29%.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A single-sided dual layer optical disc comprising: a light transmission layer; a translucent first recording layer which is accessed with a first laser beam; an space layer; and a second recording layer which is accessed with a second laser beam, these layers being arranged in that order in the direction in which a laser beam enters, the areal recording density of the second recording layer being three times or more as high as that of the first recording layer, identifying information to indicate that the first recording layer has been formed being formed in the second recording layer, the thickness of the light transmission layer from an incidence plane to the first recording layer being 550 μm or more, the thickness of the light transmission layer from the incidence plane to the second recording layer being 622 μm or less, the reflectivity of the first recording layer with respect to the first laser beam being 45% to 65%, and the reflectivity of the second recording layer with respect to the second laser beam being 15% to 29%.
2. The single-sided dual layer optical disc according to claim 1 , wherein the thickness of the light transmission layer from the incidence plane to the first recording layer is 575 μm or less, the thickness of the light transmission layer from the incidence plane to the second recording layer is 578 μm or more, and the thickness of the space layer is 28 to 47 μm.
3. The single-sided dual layer optical disc according to claim 1 or 2 , wherein the first recording layer is made of an Ag alloy film and has a thickness of 15 to 23 nm, and the second recording layer is made of an Al alloy film and has a thickness of 30 nm or less.
4. An optical disc apparatus which reads information from a single-sided dual layer optical disc which includes a light transmission layer, a translucent first recording layer which is accessed with a first laser beam, a space layer, and a second recording layer which is accessed with a second laser beam, these layers being arranged in that order in the direction in which a laser beam enters, the areal recording density of the second recording layer being three times or more as high as that of the first recording layer, identifying information to indicate that the first recording layer has been formed being formed in the second recording layer, the thickness of the light transmission layer from an incidence plane to the first recording layer being 550 μm or more, the thickness of the light transmission layer from the incidence plane to the second recording layer being 622 μm or less, the reflectivity of the first recording layer with respect to the first laser beam being 45% to 65%, and the reflectivity of the second recording layer with respect to the second laser beam being 15% to 29%, the optical disc apparatus comprising: an optical head capable of generating the first laser beam and the second laser beam; and control means for selectively causing either the first laser beam or the second laser beam to be generated.
5. The optical disc apparatus according to claim 4 , wherein the control means selects either the first laser beam or the second laser beam on the basis of a user input from a user interface.
6. The optical disc apparatus according to claim 4 or 5 , wherein the control means selects the second laser beam in an initial process of trying reading information from the installed optical disc.
7. The optical disc apparatus according to claim 6 , wherein the control means, when having succeeded in reading information in the initial process, continues selecting the second laser beam until a user input to select the first laser beam has been supplied from the user interface.
8. A reproducing method of reading information from a single-sided dual layer optical disc which includes a light transmission layer, a translucent first recording layer which is accessed with a first laser beam, an space layer, and a second recording layer which is accessed with a second laser beam, these layers being arranged in that order in the direction in which a laser beam enters, the areal recording density of the second recording layer being three times or more as high as that of the first recording layer, identifying information to indicate that the first recording layer has been formed being formed in the second recording layer, the thickness of the light transmission layer from an incidence plane to the first recording layer being 550 μm or more, the thickness of the light transmission layer from the incidence plane to the second recording layer being 622 μm or less, the reflectivity of the first recording layer with respect to the first laser beam being 45% to 65%, and the reflectivity of the second recording layer with respect to the second laser beam being 15% to 29%, the reproducing method comprising: accessing data with the second laser beam and moving the focus point back and forth in the direction of thickness of the optical disc; focusing on the second recording layer, making a gain adjustment, turning on a focus servo, and then turning on a tracking servo; reading ID of a data frame from the reproduced signal and checking the ID after turning on the tracking servo and then moving to a Control data zone in a Lead-in area; verifying information on the disc type in Physical format information in the Control data zone; and reproducing the signal in the second recording layer.
9. A reproducing method of reading information from a single-sided dual layer optical disc which includes a light transmission layer, a translucent first recording layer which is accessed with a first laser beam, an space layer, and a second recording layer which is accessed with a second laser beam, these layers being arranged in that order in the direction in which a laser beam enters, the areal recording density of the second recording layer being three times or more as high as that of the first recording layer, identifying information to indicate that the first recording layer has been formed being formed in the second recording layer, the thickness of the light transmission layer from an incidence plane to the first recording layer being 550 μm or more, the thickness of the light transmission layer from the incidence plane to the second recording layer being 622 μm or less, the reflectivity of the first recording layer with respect to the first laser beam being 45% to 65%, and the reflectivity of the second recording layer with respect to the second laser beam being 15% to 29%, the reproducing method comprising: selecting a blue-violet laser beam as a beam irradiated onto the optical disc; moving the focus point back and forth in the direction of thickness of the optical disc; focusing on the second recording layer, making a gain adjustment, turning on a focus servo, and then turning on a tracking servo; going into a state where the signal in the second recording layer is reproduced; adjusting the gain of the reproduced signal when receiving a signal to switch to the first recording layer; focusing on the first recording layer and then turning on the tracking servo; and going into a state where the signal in the first recording layer is reproduced.
10. The reproducing method according to claim 9 , further comprising: reading ID of a Data frame from the reproduced signal in the second recording layer and checking the ID after turning on the tracking servo in the second recording layer and then moving to a Control data zone in a Lead-in area; verifying information on the disc type in physical format information in the Control data zone; and reproducing the signal in the second recording layer.
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December 5, 2005
January 13, 2009
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